FMF Factory4

By silveradoss, Posted April 12, 2004

Anyone running a fmf factory4 silencer on your yz 450? If so hows the power compared to stock and did you have to rejet?

By gonzo, Posted April 12, 2004

In my experience with the FMF pipes I got more of a gain out of the header than the muffler. I bent my stocker and put the PB on as a replacement. Nice gain. I put the muffler on to match later with very little gain. Get the header first.

By azridr, Posted April 12, 2004

I've got the full Factory 4 system on my '04, and I would definately say that the power is increased throughout the powerband, but to me the most significant difference is from the mid through the top. I am able to pull gears much longer, without shifting as much. Of course, since I have the header, it is impossible to tell where the biggest change was gained, but I'm sure the muffler/midpipe play a big part. By the way, a jet kit was included, but I am trying to see how close I can leave it to stock, so I am still playing with the fuel screw. I'd be interested in hearing what others are running for jetting with this pipe.